Wireless power transmitting apparatus and method thereof

ABSTRACT

Disclosed are a wireless power transmitting apparatus and a method thereof. The wireless power transmitting apparatus wirelessly transmits power to a wireless power receiving apparatus. The wireless power transmitting apparatus detects a wireless power transmission state between the wireless power transmitting apparatus and the wireless power receiving apparatus, and generates a control signal to control transmit power based on the detected wireless power transmission state. The wireless power transmitting apparatus generates the transmit power by using first DC power based on the control signal, and transmits the transmit power to a transmission resonance coil through a transmission induction coil unit based on an electromagnetic induction scheme.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119 of KoreanPatent Application Nos. 10-2012-0027977, filed Mar. 19, 2012 and10-2012-0146956, filed Dec. 14, 2012, which are hereby incorporated byreference in their entirety.

BACKGROUND

The disclosure relates to a wireless power transmitting apparatus and amethod thereof.

A wireless power transmission or a wireless energy transfer refers to atechnology of wirelessly transferring electric energy to desireddevices. In the 1800's, an electric motor or a transformer employing theprinciple of electromagnetic induction has been extensively used andthen a method for transmitting electrical energy by irradiatingelectromagnetic waves, such as radio waves or lasers, has beensuggested. Actually, electrical toothbrushes or electrical razors, whichare frequently used in daily life, are charged based on the principle ofelectromagnetic induction. The electromagnetic induction refers to aphenomenon in which voltage is induced so that current flows when amagnetic field is varied around a conductor. Although thecommercialization of the electromagnetic induction technology has beenrapidly progressed around small-size devices, the power transmissiondistance is short.

Until now, wireless energy transmission schemes include a remotetelecommunication technology based on magnetic resonance and a shortwave radio frequency in addition to the electromagnetic induction.

Recently, among wireless power transmitting technologies, an energytransmitting scheme employing magnetic resonance has been widely used.

In a wireless power transmitting system employing magnetic resonance,since an electrical signal generated between the wireless powertransmitting apparatus and the wireless power receiving apparatus iswirelessly transferred through coils, a user may easily chargeelectronic appliances such as a portable device.

A wireless power transmitting apparatus generates AC power having aresonance frequency to be transmitted to a wireless power receivingapparatus. In this case, power transmission efficiency is determined dueto various factors. The demand for wireless power transmissionefficiency is increased.

BRIEF SUMMARY

The disclosure provides a wireless power transmitting apparatus capableof improving wireless power transmission efficiency and a methodthereof.

According to the embodiment, there is provided a wireless powertransmitting apparatus wirelessly transmitting power to a wireless powerreceiving apparatus. The wireless power transmitting apparatus includesa detector detecting a wireless power transmission state between thewireless power transmitting apparatus and the wireless power receivingapparatus, a transmit power controller generating a control signal tocontrol transmit power based on the detected wireless power transmissionstate, an AC power generator generating an AC power using first DC powerbased on the control signal, and a transmission induction coil unittransmitting the AC power to a transmission resonance coil through anelectromagnetic induction scheme.

According to the embodiment, there is provided a wireless powertransmitting apparatus wirelessly transmitting power to a wireless powerreceiving apparatus. The wireless power transmitting apparatus includesa transmission induction coil transmitting power applied thereto to atransmission resonance coil through an electromagnetic induction scheme,a transistor circuit unit having a full-bridge structure and connectedto the transmission induction coil, a detector detecting a wirelesspower transmission state between the wireless power transmittingapparatus and the wireless power receiving apparatus, and a transmitpower controller controlling the transistor circuit unit having thefull-bridge structure based on the detected wireless power transmissionstate.

As described above, according to the embodiment, the efficiency of thewireless power transmitting apparatus can be increased.

In addition, according to the embodiment, circuits can be inhibited frombeing destroyed due to high current.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a wireless power system according to oneembodiment.

FIG. 2 is a circuit diagram showing an equivalent circuit of thetransmission induction coil unit according to the one embodiment.

FIG. 3 is a circuit diagram showing an equivalent circuit of a powersupply device and a wireless power transmitting apparatus according toone embodiment.

FIG. 4 is a circuit diagram showing an equivalent circuit of a wirelesspower receiving apparatus according to one embodiment.

FIG. 5 is a block diagram showing the power supply device according toone embodiment.

FIG. 6 is a block diagram showing an AC power generator and a transmitpower controller according to one embodiment.

FIG. 7 is a circuit diagram showing a DC-DC converter according to oneembodiment.

FIG. 8 is a circuit diagram showing the DC-AC converter and the powertransmission state detector according to one embodiment.

FIG. 9 is a flowchart showing a wireless power transmitting methodaccording to one embodiment

FIG. 10 shows waveforms of voltage at each node in the power supplydevice according to one embodiment.

FIG. 11 is a block diagram showing a power supply device according toanother embodiment.

FIG. 12 is a block diagram showing an AC power generator and a transmitpower controller according to another embodiment.

FIG. 13 is a circuit diagram showing a DC-AC converter and a powertransmission state detector according to another embodiment.

FIG. 14 is a flowchart showing a wireless power transmitting methodaccording to another embodiment

FIG. 15 shows waveforms of voltage at each node in the power supplydevice according to another embodiment.

FIG. 16 is a block diagram showing a power supply device according tostill another embodiment.

FIG. 17 is a block diagram showing an AC power generator and a transmitpower controller according to still another embodiment.

FIG. 18 is a circuit diagram showing a DC-AC converter and a powertransmission state detector according to still another embodiment.

FIG. 19 is a flowchart showing a wireless power transmitting methodaccording to still another embodiment.

DETAILED DESCRIPTION

Hereinafter, embodiments will be described in detail with reference toaccompanying drawings so that those skilled in the art can easily workwith the embodiments. However, the embodiments may not be limited tothose described below, but have various modifications. The elements,which are not concerned with the description of the embodiments in thedrawings, may be omitted for the purpose of convenience or clarity. Thesame reference numbers will be assigned the same elements throughout thedrawings.

In the following description, when a predetermined part “includes” apredetermined component, the predetermined part does not exclude othercomponents, but may further include other components unless indicatedotherwise.

Hereinafter, a wireless power transmitting system according to oneembodiment will be described with reference to FIGS. 1 to 4.

FIG. 1 is a view showing a wireless power system according to oneembodiment.

Referring to FIG. 1, the wireless power transmitting system may includea power supply device 100, a wireless power transmitting apparatus 200,a wireless power receiving apparatus 300 and a load 400.

According to one embodiment, the power supply device 100 may be includedin the wireless power transmitting apparatus 200.

The wireless power transmitting apparatus 200 may include a transmissioninduction coil unit 210 and a transmission resonant coil unit 220.

The wireless power receiving apparatus 300 may include a receptionresonant coil unit 310, a reception induction coil unit 320, and arectifying unit 330.

Both terminals of the power supply device 100 are connected to bothterminals of the transmission induction coil unit 210.

The transmission resonant coil unit 220 may be spaced apart from thetransmission induction coil unit 210 by a predetermined distance.

The reception resonant coil unit 310 may be spaced apart from thereception induction coil unit 320 by a predetermined distance.

Both terminals of the reception induction coil unit 320 are connected toboth terminals of the rectifying unit 330, and the load 400 is connectedto both terminals of the rectifying unit 330. According to oneembodiment, the load 400 may be included in the wireless power receivingapparatus 300.

The power generated from the power supply device 100 is transmitted tothe wireless power transmitting apparatus 200. The power received in thewireless power transmitting apparatus 200 is transmitted to the wirelesspower receiving apparatus 300 that makes resonance with the wirelesspower transmitting apparatus 200 due to a resonance phenomenon, that is,has the resonance frequency the same as that of the wireless powertransmitting apparatus 200.

Hereinafter, the power transmission process will be described in moredetail.

The power supply device 100 generates AC power having a predeterminedfrequency and transmits the AC power to the wireless power transmittingapparatus 200.

The transmission induction coil unit 210 and the transmission resonantcoil unit 220 are inductively coupled with each other. In other words,if AC current flows through the transmission induction coil unit 210 dueto the power received from the power supply apparatus 100, the ACcurrent is induced to the transmission resonant coil unit 220 physicallyspaced apart from the transmission induction coil unit 210 due to theelectromagnetic induction.

Thereafter, the power received in the transmission resonant coil unit220 is transmitted to the wireless power receiving apparatus 300, whichmakes a resonance circuit with the wireless power transmitting apparatus200, through resonance.

Power can be transmitted between two LC circuits, which areimpedance-matched with each other, through resonance. The powertransmitted through the resonance can be farther transmitted with higherefficiency when comparing with the power transmitted by theelectromagnetic induction.

The reception resonant coil unit 310 receives power from thetransmission resonant coil unit 220 through the resonance. The ACcurrent flows through the reception resonant coil unit 310 due to thereceived power. The power received in the reception resonant coil unit310 is transmitted to the reception induction coil unit 320, which isinductively coupled with the reception resonant coil unit 310, due tothe electromagnetic induction. The power received in the receptioninduction coil unit 320 is rectified by the rectifying unit 330 andtransmitted to the load 400.

According to one embodiment, the transmission induction coil unit 210,the transmission resonant coil unit 220, the reception resonant coilunit 310, and the reception resonant coil unit 320 may have the shape ofa circle, an oval, or a rectangle, but the embodiment is not limitedthereto.

The transmission resonant coil unit 220 of the wireless powertransmitting apparatus 200 may transmit power to the reception resonantcoil unit 310 of the wireless power receiving apparatus 300 through amagnetic field.

In detail, the transmission resonant coil unit 220 and the receptionresonant coil unit 310 are resonance-coupled with each other so that thetransmission resonant coil unit 220 and the reception resonant coil unit310 operate at a resonance frequency.

The resonance-coupling between the transmission resonant coil unit 220and the reception resonant coil unit 310 can significantly improve thepower transmission efficiency between the wireless power transmittingapparatus 200 and the wireless power receiving apparatus 300.

A quality factor and a coupling coefficient are important in thewireless power transmission. In other words, the power transmissionefficiency can be gradually improved as the values of the quality factorand the coupling coefficient are increased.

The quality factor may refer to an index of energy that may be stored inthe vicinity of the wireless power transmitting apparatus 200 or thewireless power receiving apparatus 300.

The quality factor may vary according to the operating frequency w aswell as a shape, a dimension and a material of a coil. The qualityfactor may be expressed as following equation, Q=ω*L/R. In the aboveequation, L refers to the inductance of a coil and R refers toresistance corresponding to the quantity of power loss caused in thecoil.

The quality factor may have a value of 0 to infinity. The powertransmission efficiency between the wireless power transmittingapparatus 200 and the wireless power receiving apparatus 300 can beimproved as the value of the quality factor is increased.

The coupling coefficient represents the degree of magnetic couplingbetween a transmission coil and a reception coil, and has a value of 0to 1.

The coupling coefficient may vary according to the relative position andthe distance between the transmission coil and the reception coil.

FIG. 2 is a circuit diagram showing an equivalent circuit of thetransmission induction coil unit 210 according to the one embodiment.

As shown in FIG. 2, the transmission induction coil unit 210 may includean inductor L1 and a capacitor C1, and a circuit having a desirableinductance and a desirable capacitance can be constructed by theinductor L1 and the capacitor C1.

The transmission induction coil unit 210 may be constructed as anequivalent circuit in which both terminals of the inductor L1 areconnected to both terminals of the capacitor C1. In other words, thetransmission induction coil unit 210 may be constructed as an equivalentcircuit in which the inductor L1 is connected to the capacitor C1 inparallel.

The capacitor C1 may include a variable capacitor, and impedancematching may be performed by adjusting the capacitance of the capacitorC1. The equivalent circuit of each of the transmission resonant coilunit 220, the reception resonant coil unit 310 and the receptioninduction coil unit 320 may be the same as the equivalent circuit shownin FIG. 2.

FIG. 3 is a circuit diagram showing an equivalent circuit of the powersupply device 100 and the wireless power transmitting apparatus 200according to one embodiment.

As shown in FIG. 3, the transmission induction coil unit 210 includesthe inductor L1 having predetermined inductance and a capacitor C1having predetermined capacitance. The transmission resonant coil unit220 includes an inductor L2 having predetermined inductance and acapacitor C2 having predetermined capacitance.

FIG. 4 is a circuit diagram showing an equivalent circuit of thewireless power receiving apparatus 300 according to one embodiment.

As shown in FIG. 4, the reception resonant coil unit 310 includes aninductor L3 having predetermined inductance and a capacitor C1 havingpredetermined capacitance. The reception induction coil unit 320includes an inductor L4 having predetermined inductance and a capacitorC4 having predetermined capacitance.

The rectifying unit 330 may transfer converted DC power to the load 400by converting AC power received from the reception induction coil unit320 into the DC power.

In detail, the rectifying unit 330 may include a rectifier and asmoothing circuit. According to one embodiment, the rectifier mayinclude a silicon rectifier and may be equivalent as a diode D1 as shownin FIG. 4.

The rectifier may convert AC power received from the reception inductioncoil unit 320 into the DC power.

The smoothing circuit may output smooth DC power by removing ACcomponents from the DC power converted by the rectifier. According toone embodiment, as shown in FIG. 4, the smoothing circuit may include arectifying capacitor C5, but the embodiment is not limited thereto.

The load 400 may be a predetermined rechargeable battery or a devicerequiring the DC power. For example, the load 400 may refer to abattery.

The wireless power receiving apparatus 300 may be installed in anelectronic device, such as a cellular phone, a laptop computer or amouse, requiring the power. Accordingly, the reception resonant coilunit 310 and the reception induction coil unit 320 may have the shapesuitable to the shape of the electronic device.

The wireless power transmitting apparatus 200 may interchangeinformation with the wireless power receiving apparatus 300 throughin-band communication or out-of-band communication.

The in-band communication refers to the communication for interchanginginformation between the wireless power transmitting apparatus 200 andthe wireless power receiving apparatus 300 through a signal having thefrequency used in the wireless power transmission. The wireless powerreceiving apparatus 300 may further include a switch, and may receive ormay not receive power transmitted from the wireless power transmittingapparatus 200 through a switching operation of the switch. Accordingly,the wireless power transmitting apparatus 200 can recognize an on-signalor an off-signal of the switch included in the wireless power receivingapparatus 300 by detecting the quantity of power consumed in thewireless power transmitting apparatus 200.

In detail, the wireless power receiving apparatus 300 may change thepower consumed in the wireless power transmitting apparatus 200 byadjusting the quantity of power absorbed in a resistor by using theresistor and the switch. The wireless power transmitting apparatus 200may acquire the state information of the wireless power receivingapparatus 300 by detecting the variation of the power consumption. Theswitch may be connected to the resistor in series. According to oneembodiment, the state information of the wireless power receivingapparatus 300 may include information about the present charge quantityin the wireless power receiving apparatus 300 and the change of thecharge quantity.

In more detail, if the switch is open, the power absorbed in theresistor becomes zero, and the power consumed in the wireless powertransmitting apparatus 200 is reduced.

If the switch is short-circuited, the power absorbed in the resistorbecomes greater than zero, and the power consumed in the wireless powertransmitting apparatus 200 is increased. If the wireless power receivingapparatus repeats the above operation, the wireless power transmittingapparatus 200 detects power consumed therein to make digitalcommunication with the wireless power receiving apparatus 300.

The wireless power transmitting apparatus 200 receives the stateinformation of the wireless power receiving apparatus 300 through theabove operation so that the wireless power transmitting apparatus 200can transmit appropriate power.

On the contrary, the wireless power transmitting apparatus 200 mayinclude a resistor and a switch to transmit the state information of thewireless power transmitting apparatus 200 to the wireless powerreceiving apparatus 300. According to one embodiment, the stateinformation of the wireless power transmitting apparatus 200 may includeinformation about the maximum quantity of power to be supplied from thewireless power transmitting apparatus 200, the number of wireless powerreceiving apparatus 300 receiving the power from the wireless powertransmitting apparatus 200 and the quantity of available power of thewireless power transmitting apparatus 200.

Hereinafter, the out-of-band communication will be described.

The out-of-band communication refers to the communication performedthrough a specific frequency band other than the resonance frequencyband in order to interchange information necessary for the powertransmission. The wireless power transmitting apparatus 200 and thewireless power receiving apparatus 300 can be equipped with out-of-bandcommunication modules to interchange information necessary for the powertransmission. The out-of-band communication module may be installed inthe power supply device. In one embodiment, the out-of-bandcommunication module may use a short-distance communication technology,such as Bluetooth, Zigbee, WLAN or NFC, but the embodiment is notlimited thereto.

Hereinafter, the power supply device 100 according to one embodimentwill be described with reference to FIGS. 5 to 10.

FIG. 5 is a block diagram showing the power supply device 100 accordingto one embodiment.

As shown in FIG. 5, the power supply device 100 according to oneembodiment includes a power supply 110, an oscillator 130, an AC powergenerator 150, a power transmission state detector 180, and a transmitpower controller 190. In addition, the power supply device 100 isconnected with the wireless power transmitting apparatus 200.

The power supply 110 generates DC power having DC voltage and outputsthe DC power through an output terminal thereof.

The oscillator 130 generates a lower-power sine wave signal.

The power transmission state detector 180 detects a wireless powertransmission state between the wireless power transmitting apparatus 200and the wireless power transmitting apparatus 300.

The transmit power controller 190 generates a control signal to controlthe AC power generator 150 based on the detected wireless powertransmission state.

The AC power generator 150 generates an AC power. At this time, the ACpower can have various waveforms such as a rectangular-waveform,sinusoidal-waveform, or etc. In particular, the AC power generator 150generates AC power having rectangular-waveform voltage by amplifying thelower-power sine wave signal of the oscillator 130 using DC power of thepower supply 110 based on the control signal of the transmit powercontroller 190.

The wireless power transmitting apparatus 200 transmits the output powerof the AC power generator 150 to the wireless power receiving apparatus300 by resonance.

FIG. 6 is a block diagram showing the AC power generator 150 and thetransmit power controller 190 according to one embodiment.

As shown in FIG. 6, the AC power generator 150 according to oneembodiment includes AC power generation controller 151, a DC-ACconverter 153, and a DC-DC converter 155, and the transmit powercontroller 190 includes a DC power generation controller 191 and astorage unit 192.

The AC power generation controller 151 generates an AC power generationcontrol signal based on the lower-power sine wave signal of theoscillator 130.

The DC power generation controller 191 generates a DC power generationcontrol signal based on the detected wireless power transmission stateso that the DC-DC converter 155 may output power having output currentin a target current range and target DC voltage.

The storage unit 192 stores a look-up table.

The DC-DC converter 155 converts the output power of the power supply110 into DC power, which has output current in the target current rangeand the target DC voltage, based on the DC power generation controlsignal.

The DC-AC converter 153 converts the output power of the DC-DC converter155 into AC power having the rectangular-waveform AC voltage based onthe AC power generation control signal, and outputs the power to thetransmission induction coil unit 210.

FIG. 7 is a circuit diagram showing the DC-DC converter 155 according toone embodiment.

As shown in FIG. 7, the DC-DC converter 155 includes an inductor L11, apower switch T11, a diode D11, and a capacitor C11. The power switch T11may be realized by using a transistor. In particular, the power switchT11 may include an n-channel metal-oxide-semiconductor field-effecttransistor (NMOSFET), but may be substituted with another deviceperforming the same function.

One terminal of the inductor L11 is connected with an output terminal ofthe power supply 110, and an opposite terminal of the inductor L11 isconnected with a drain electrode of the power switch T11.

The gate electrode of the power switch T11 is connected with an outputterminal of the DC power generation controller 191, and a sourceelectrode of the power switch T11 is connected with the ground.

An anode electrode of the diode D11 is connected with the drainelectrode of the power switch T11.

One terminal of the capacitor C11 is connected with the cathodeelectrode of the diode D11, and an opposite terminal of the capacitorC11 is connected with the ground.

FIG. 8 is a circuit diagram showing the DC-AC converter 153 and thepower transmission state detector 180 according to one embodiment.

As shown in FIG. 8, the DC-AC converter 153 includes a transistorcircuit unit having a half-bridge structure. The half-bridge transistorcircuit includes an upper transistor T21, a lower transistor T22, and aDC cut-off capacitor C21, and is connected to the AC power generationcontroller 151 and the transmission induction coil unit 210. The powertransmission state detector 180 includes a resistor R1 and a voltagedifference measuring unit 181, and is connected with the DC-DC converter155, the DC-AC converter 153, and the DC power generation controller191. The DC-AC converter 153 is connected with the DC-DC converter 155through the resistor R1. The upper and lower transistors T21 and T22 mayinclude n-channel metal-oxide-semiconductor field-effect transistor(NMOS), but may be substituted with another device performing the samefunction.

The AC power generation controller 151 has an output terminal for anupper transistor control signal and an output terminal for a lowertransistor control signal, and outputs the AC power generation controlsignal based on the lower-power sine wave signal. The AC powergeneration controller 151 generates the upper transistor control signalas the AC power generation control signal based on the lower-power sinewave signal of the oscillator 130, and outputs the upper transistorcontrol signal through the output terminal for the upper transistorcontrol signal. The AC power generation controller 151 generates thelower transistor control signal as the AC power generation controlsignal based on the lower-power sine wave signal of the oscillator 130,and outputs the lower transistor control signal through the outputterminal for the lower transistor control signal.

A drain electrode of the upper transistor T21 is connected with oneterminal of the resistor R1, and the gate electrode is connected withthe output terminal for the upper transistor control signal of the ACpower generation controller 151.

A drain electrode of the lower transistor T22 is connected with a sourceelectrode of the upper transistor T21, a gate electrode of the lowertransistor T22 is connected with the output terminal for the lowertransistor control signal of the AC power generation controller 151, anda source electrode of the lower transistor T22 is connected with theground.

One terminal of the DC cut-off capacitor C21 is connected with thesource electrode of the upper transistor T21, and an opposite terminalof the DC cut-off capacitor C21 is connected with one terminal of theinductor L1. An opposite terminal of the inductor L1 is connected withthe ground.

The voltage difference measuring unit 181 measures the differencebetween voltages applied to both terminals of the resistor R1.

Hereinafter, a wireless power transmitting method according to oneembodiment will be described with reference to FIGS. 9 and 10.

FIG. 9 is a flowchart showing the wireless power transmitting methodaccording to one embodiment, and FIG. 10 shows waveforms of voltage ateach node in the power supply device 100 according to one embodiment.

In particular, FIG. 9 shows the wireless power transmitting method toexplain the embodiments of FIGS. 6 to 8 in detail.

The power supply 110 generates DC power having DC voltage (step S101).In particular, the power supply 110 may convert AC power having ACvoltage into the DC power having DC voltage.

The oscillator 130 generates the lower-power sine wave signal (stepS103).

The power transmission state detector 180 detects the wireless powertransmission state (step S105). The power transmission state detector180 may detect the wireless power transmission state based on the levelof the output current of the DC-DC converter 155. Since the voltagesapplied to the both terminal of the resistor R1 are proportional to thelevel of the output current of the DC-DC converter 155, the voltagedifference measuring unit 181 of the power transmission state detector180 may detect the wireless power transmission state based on thedifferent between the voltages applied to both terminals of the resistorR1.

Since the coupling coefficient varies depending on the distance betweenthe wireless power transmitting apparatus 200 and the wireless powerreception apparatus 300 or the relatively positions thereof, thewireless power transmission state may be changed. In other words, as thedistance between the distance between the wireless power transmittingapparatus 200 and the wireless power reception apparatus 300 isincreased, the coupling coefficient is reduced, so that the wirelesspower transmission state may be degraded. As the wireless powertransmission state becomes degraded, even if the wireless powertransmitting apparatus 200 transmits power having the same intensity tothe wireless power receiving apparatus 300, greater power is consumeddue to the inferior transmission efficiency. Therefore, the powertransmission state detector 180 may detect the wireless powertransmission state based on the level of the output current of the DC-DCconverter 155.

Since the output current of the DC-DC converter 155 may not beconstantly maintained, the power transmission state detector 180 maymeasure the peak-to-peak value of the output current of the DC-DCconverter 155.

The DC power generation controller 191 generates a DC power generationcontrol signal based on the detected wireless power transmission stateso that the DC-DC converter 155 may output DC power having outputcurrent in a target current range and target DC voltage (step S107), andoutputs the DC power generation control signal to the gate electrode ofthe transistor T11. In this case, the target current range may have aconstant value regardless of the level of the target DC voltage, or mayvary depending on the level of the target DC voltage. In addition, thetarget current range may be the range of the peak-to-peak value of thetarget current. As shown in FIG. 10, the DC power generation controlsignal may be a pulse width modulation (PWM) signal continuouslyrepresented throughout the whole duration. The DC power generationcontroller 191 may determine a duty ratio of the PWM signal based on thedetected wireless power transmission state.

According to one embodiment, the voltage difference measuring unit 181obtains a measurement output current value based on the differencebetween voltages applied to both terminals of the resistor R1.Thereafter, if the measurement output current value gets out of thereference range, the DC power generation controller 191 changes the dutyrate, and outputs the DC power generation control signal serving as thePWM signal having the changed duty rate to the gate electrode of thetransistor T11 so that the output current value of the DC-DC converter155 becomes in the reference range. In detail, if the measurement outputcurrent value is greater than the upper limit of the reference range,the DC power generation controller 191 reduces the duty rate and outputsthe DC power generation control signal serving as the PWM signal havingthe reduced duty rate to the gate electrode of the transistor T11 sothat the output current value of the DC-DC converter 155 becomes in thereference range. Further, if the measurement output current value issmaller than the lower limit of the reference range, the DC powergeneration controller 191 increases the duty rate and outputs the DCpower generation control signal serving as the PWM signal having theincreased duty rate to the gate electrode of the transistor T11 so thatthe output current value of the DC-DC converter 155 becomes in thereference range.

According to another embodiment, the storage unit 192 may have a look-uptable representing the relationship between a plurality of measurementoutput power values and a plurality of target output voltage values.Table 1 shows the look-up table representing the relationship betweenthe measurement output power values and the target output voltage valuesaccording to one embodiment.

TABLE 1 Measurement Output Power Target Output Voltage 10 W or less 12 V10~12 W 14 V 12~14 W 16 V 14~16 W 18 V 16~18 W 20 V 18~20 W 22 V 20 W ormore 24

In this case, the voltage difference measuring unit 181 obtains ameasurement output current value based on the difference betweenvoltages applied to both terminals of the resistor R1. Thereafter, theDC power generation controller 191 obtains a measurement output powervalue of present output power of the DC-DC converter 155 based on themeasurement output current value, and searches for a target outputvoltage value corresponding to the measurement output power value in thelook-up table. Then, the duty rate of the PWM signal is determined usingthe voltage of the node B as feed-back information so that the outputvoltage of the DC-DC converter 155 may have the target output voltagevalue, and the DC power generation control signal may be generated basedon the duty rate.

According to another embodiment, the storage unit 192 may have a look-uptable representing the relationship between a plurality of measurementoutput current values and a plurality of target output voltage values.In this case, the voltage difference measuring unit 181 obtains ameasurement output current value based on the difference betweenvoltages applied to both terminals of the resistor R1. Thereafter, theDC power generation controller 191 searches for a target output voltagevalue corresponding to the measurement output current value in thelook-up table. Then, the duty rate of the PWM signal is determined usingthe voltage of the node B as feed-back information so that the outputvoltage of the DC-DC converter 155 may have the target output voltagevalue, and the DC power generation control signal may be generated basedon the duty rate.

Table 2 shows a look-up table according to one embodiment.

TABLE 2 Measurement output current at initial output Coupling Targetoutput Desirable voltage coefficient voltage current range 100 mA orless 0.03 or less 30 V 801~851 mA 101~150 mA 0.05 28 V 751~800 mA151~200 mA 0.08 26 V 701~751 mA 201~250 mA 0.11 24 V 651~700 mA 251~300mA 0.14 22 V 601~650 mA 301~350 mA 0.17 20 V 551~600 mA 351 mA or more0.20 or more 18 V 501~550 mA

As shown in table 2, the storage unit 192 may have a look-up tablecorresponding to an output current value of the DC-DC converter 155, acoupling coefficient, an output voltage value of the DC-DC converter155, and a desirable current range.

If the level of the output current of the DC-DC converter 155 is 100 mAor more when the DC-DC converter 155 outputs DC power having an initialoutput voltage value, the wireless power receiving apparatus 300 may beregarded as being detected. The initial output voltage may be 12V whichis given for the illustrative purpose.

If the level of the output current of the DC-DC converter 155 is 120 mAwhen the DC-DC converter 155 outputs the DC power having the initialoutput voltage value, the coupling coefficient between the transmissionresonance coil unit 220 of the wireless power transmitting apparatus 200and the reception resonance coil unit 310 of the wireless powerreceiving apparatus 300 corresponds to 0.05. In this case, the DC powergeneration controller 191 determines the wireless power receivingapparatus 300 as being apart from the wireless power transmittingapparatus 200 and controls the DC-DC converter 155 to have the outputvoltage of 28V.

Thereafter, when the level of the output voltage of the DC-DC converter155 is maintained at 28V, the DC power generation controller 191determines if the level of the output current of the DC-DC converter 155is in a desirable current range of 751 mA to 800 mA.

If the level of the output current of the DC-DC converter 155 is out ofthe desirable current range, the DC power generation controller 191controls the DC-DC converter 155 so that the level of the output voltageof the DC-DC converter 155 is the level (12V) of the initial outputvoltage. If the level of the output current of the DC-DC converter 155is 180 mA, the controller 270 determines the wireless power transmittingapparatus 200 as being closer to the wireless power receiving apparatus300 when comparing with the case that the level of the output current ofthe DC-DC converter 155 is 120 mA. Accordingly, the controller 270controls the DC-DC converter 155 such that the level of the outputvoltage of the DC-DC converter 155 is 26V.

Although the above example has been described in that the distancebetween the wireless power transmitting apparatus 200 and the wirelesspower receiving apparatus 300 is related to the intensity of current,various wireless power states such as a direction in which the wirelesspower transmitting apparatus 200 and the wireless power receivingapparatus 300 are placed may be considered.

As described above, the wireless power transmitting apparatus 200adjusts power transmitted to the wireless power receiving apparatus 300based on the various wireless power transmission states such as thedistance from the wireless power receiving apparatus 300 and thedirection in which the wireless power receiving apparatus 300 is placed,thereby maximizing the power transmission efficiency, and presenting thepower loss.

The DC-DC converter 155 converts the output power of the power supply110 into the DC power having the output current in the target currentrange and the target DC voltage based on the DC power generation controlsignal (step S109). The level of the output voltage of the DC-DCconverter 155 may be equal to that of the output voltage of the powersupply 110, or greater than or smaller than that of the output voltageof the power supply 110.

The AC power generation controller 151 generates an AC power generationcontrol signal based on the sin-wave lower power of the oscillator 130(step S111). The AC power generation controller 151 may generate theupper transistor control signal serving as the AC power generationcontrol signal based on the sin-wave lower power of the oscillator 130,and may output the upper transistor control signal through the outputterminal for the upper transistor control signal. The AC powergeneration controller 151 may generate the lower transistor controlsignal serving as the AC power generation control signal based on thesin-wave lower power of the oscillator 130, and may output the lowertransistor control signal through the output terminal for the lowertransistor control signal.

Hereinafter, the upper and lower transistor control signals will bedescribed with reference to FIG. 10.

As shown in FIG. 10, the upper and lower transistor control signals havethe rectangular waveform.

One period of the upper transistor control signal sequentially includesa turn-on time slot of the upper transistor T21 and a turn-off time slotof the upper transistor T21. The turn-on time slot of the uppertransistor T21 may correspond to one half period of the lower-power sinewave signal of the oscillator 130, and the turn-off time slot of theupper transistor T21 may correspond to the other half period of thelower-power sine wave signal.

One period of the lower transistor control signal sequentially includesa turn-on time slot of the lower transistor T22 and a turn-off time slotof the lower transistor T22. The turn-on time slot of the lowertransistor T22 may correspond to one half period of the lower-power sinewave signal of the oscillator 130, and the turn-off time slot of thelower transistor T22 may correspond to the other half period of thelower-power sine wave signal.

The upper transistor control signal has a level to turn on the uppertransistor T21 during the turn-on time slot of the upper transistor T21.The level to turn on the upper transistor T21 may be a high level.

During the turn-off time slot of the upper transistor T21, the uppertransistor control signal has a level to turn off the upper transistorT21. The level to turn off the upper transistor T21 may be a low level.

During the turn-on time slot of the lower transistor T22, the lowertransistor control signal has a level to turn on the lower transistorT22. The level to turn on the lower transistor T22 may be a high level.

During the turn-off time slot of the lower transistor T22, the lowertransistor control signal has a level to turn off the lower transistorT22. The level to turn off the lower transistor T22 may be a low level.

During the turn-on time slot of the upper transistor T21, the lowertransistor control signal has the level to turn off the lower transistorT22 during the turn-off time slot of the lower transistor T22.

During the turn-on time slot of the lower transistor T22, the lowertransistor control signal has the level to turn off the lower transistorT22 during the turn-off time slot of the upper transistor T21.

In order to inhibit a short circuit occurring by simultaneously turningon the upper and the lower transistors T21 and T22, the upper and lowertransistor control signals may have a dead time slot.

In order to output power of voltage provided in a rectangular waveformhaving the duty cycle of 50%, the turn-on time slot of the uppertransistor T21 has a duration corresponding to (50-a) % of one period(T), and the dead time slot of the upper transistor T21 has the durationof a % of one period (T). The turn-off time slot of the upper transistorT21 may have a duration corresponding to 50% of one period (T), theturn-on time slot of the lower transistor T22 may have a durationcorresponding to (50-a) % of one period (T), the dead time slot of thelower transistor T22 may have a duration corresponding to a % of oneperiod (T), and the turn-off time slot of the lower transistor T22 mayhave a duration corresponding to 50% of one period (T). For example, “a”may be 1%.

The DC-AC converter 153 converts the output power of the DC-DC converter155 into AC power having rectangular-waveform AC voltage based on the ACpower generation control signal (step S113) and outputs the AC power tothe transmission induction coil unit 210.

Hereinafter, the operation of the DC-AC converter 153 will be describedwith reference to FIG. 10.

The upper and lower transistors T21 and T22 output rectangular-waveformpower having rectangular-waveform voltage V3 shown in FIG. 10 accordingto the upper and lower transistor control signals having the dead timeslot.

The DC cut-off capacitor C21 cuts off DC voltage of therectangular-waveform power and outputs the rectangular-waveform powerhaving the rectangular-waveform AC voltage V4 to the transmissioninduction coil unit 210.

The wireless power transmitting apparatus 200 transmits therectangular-waveform AC power having the rectangular-waveform AC voltageto the wireless power receiving apparatus 300 by resonance (step S115).

Hereinafter, a power supply device 100 according to another embodimentwill be described with reference to FIGS. 11 to 15.

FIG. 11 is a block diagram showing the power supply device 100 accordingto another embodiment.

As shown in FIG. 11, the power supply device 100 according to anotherembodiment includes the power supply 110, the oscillator 130, an ACpower generator 160, the power transmission state detector 180, and thetransmit power controller 190. In addition, the power supply device 100is connected with the wireless power transmitting apparatus 200.

The power supply 110 generates DC power having DC voltage and outputsthe DC power through an output terminal thereof.

The oscillator 130 generates a lower-power sine wave signal.

The power transmission state detector 180 detects the wireless powertransmission state.

The transmit power controller 190 generates a control signal to controlthe AC power generator 160 based on the detected wireless powertransmission state and the lower-power sine wave signal of theoscillator 130.

The AC power generator 160 generates AC power havingrectangular-waveform voltage by amplifying the lower-power sine wavesignal of the oscillator 130 using DC power of the power supply 110based on the control signal of the transmit power controller 190.

The wireless power transmitting apparatus 200 transmits the output powerof the AC power generator 160 to the wireless power receiving apparatus300 by resonance.

FIG. 12 is a block diagram showing the AC power generator 160 and thetransmit power controller 190 according to another embodiment.

As shown in FIG. 12, the AC power generator 160 according to anotherembodiment includes a DC-AC converter 163, and the transmit powercontroller 190 includes an AC power generation controller 193.

The AC power generation controller 193 generates an AC power generationcontrol signal based on the lower-power sine wave signal of theoscillator 130. In addition, the AC power generation controller 193 maygenerate the AC power generation control signal, which allows the powersupply 110 to output DC power having output current in a target currentrange, based on the detected wireless power transmission state. Thetarget current range may be the range of the peak-to-peak value of thetarget current.

The DC-AC converter 163 converts the output power of the power supply110 into AC power having rectangular-waveform AC voltage based on the ACpower generation control signal, and outputs the AC power to thetransmission induction coil unit 210.

FIG. 13 is a circuit diagram showing the DC-AC converter 163 and thepower transmission state detector 180.

As shown in FIG. 13, the DC-AC converter 163 includes a full-bridgetransistor circuit unit. The full-bridge transistor circuit unitincludes two half-bridge transistor circuits. One of the two half-bridgetransistor circuits includes upper and lower transistors T41 and T42,and the other includes upper and lower transistors T44 and T43. Theupper transistors T41 and T44, and the lower transistors T42 and T43 maybe n-channel metal-oxide-semiconductor field-effect transistors(NMOS-FETs), and may be substituted with different devices performingthe same operation.

The power transmission state detector 180 includes a resistor R1 and thevoltage difference measuring unit 181, and is connected to the powersupply 110, the DC-AC converter 163, and the AC power generationcontroller 193. The DC-AC converter 163 is connected to the power supply110 through the resistor R1.

The AC power generation controller 193 has first and second uppertransistor control signal output terminals and first and second lowertransistor control signal output terminals, and generates an AC powergeneration control signal based on the lower-power sine wave signal ofthe oscillator 130 and a wireless power transmission state.

A drain electrode of the upper transistor T41 is connected with oneterminal of the resistor R1, a gate electrode of the upper transistorT41 is connected with the first upper transistor control signal outputterminal of the AC power generation controller 193, and a sourceelectrode of the upper transistor T41 is connected with one terminal ofthe inductor L1.

A drain electrode of the lower transistor T42 is connected with thesource electrode of the upper transistor T41, a gate electrode of thelower transistor T42 is connected to the first lower transistor controlsignal output terminal of the AC power generation controller 193, and asource electrode of the lower transistor T42 is connected with theground.

A drain electrode of the upper transistor T44 is connected with oneterminal of the resistor R1, a gate electrode of the upper transistorT44 is connected with the second upper transistor control signal outputterminal of the AC power generation controller 193, and a sourceelectrode of the upper transistor T44 is connected with an oppositeterminal of the inductor L1.

A drain electrode of the lower transistor T43 is connected with thesource electrode of the upper transistor T44, a gate electrode of thelower transistor T43 is connected to the second lower transistor controlsignal output terminal of the AC power generation controller 193, and asource electrode of the lower transistor T43 is connected with theground.

The voltage difference measuring unit 181 measures the differencebetween voltages applied to both terminals of the resistor R1.

Hereinafter, a wireless power transmitting method will be described withreference to FIGS. 14 and 15 according to another embodiment.

FIG. 14 is a flowchart showing the wireless power transmitting methodaccording to another embodiment, and FIG. 15 shows waveforms of voltageat each node in the power supply device 100 according to anotherembodiment.

In particular, FIG. 14 shows the wireless power transmitting method toexplain the embodiments of FIGS. 11 to 13 in detail.

The power supply 110 generates DC power having DC voltage (step S301).In particular, the power supply 110 may convert AC power having ACvoltage into the DC power having DC voltage.

The oscillator 130 generates a lower-power sine wave signal (step S303).

The power transmission state detector 180 detects the wireless powertransmission state (step S305). The power transmission state detector180 may detect the wireless power transmission state based on the levelof the output current of the power supply 110. Since the voltagesapplied to the both terminal of the resistor R1 are proportional to thelevel of the output current of the power supply 110, the voltagedifference measuring unit 181 of the power transmission state detector180 may detect the wireless power transmission state based on thedifferent between the voltages applied to both terminals of the resistorR1. Since the output current of the power supply 110 may not beconstantly maintained, the power transmission state detector 180 maymeasure the wireless power transmission state based on the peak-to-peaklevel of the output current of the power supply 110.

The AC power generation controller 193 generates the AC power generationcontrol signal allowing the power supply 110 to output DC power havingthe output current in the target current range, based on the detectedwireless power transmission state (step S311), and outputs the generatesthe AC power generation control signal to the DC-AC converter 163. Sincethe output current of the power supply 110 may not be constantlymaintained, the power transmission state detector 180 may measure thepeak-to-peak level of the output current of the power supply 110.

According to one embodiment, the AC power generation controller 193 maydetermine an operating mode of the DC-AC converter 163 based on thedetected wireless power transmission state, and may output the AC powergeneration control signal for the operating mode to the DC-AC converter163. In this case, the operating mode may be one of a full-bridgeoperating mode and a half-bridge operating mode. The voltage differencemeasuring unit 181 obtains a measurement output current value based onthe difference between voltages applied to both terminals of theresistor R1. The DC power generation controller 191 may compare themeasurement output current value with a reference value and determinethe operating mode of the DC-AC converter 163 according to thecomparison result. In this case, the reference value may be in thedesirable current range of table 2 set according to the initial outputvoltage values.

If the measurement output current value is greater than the referencevalue, the DC power generation controller 191 may determine theoperating mode of the DC-AC converter 163 as the full-bridge operatingmode. If the measurement output current value is smaller than thereference value, the DC power generation controller 191 may determinethe operating mode of the DC-AC converter 163 as the half-bridgeoperating mode.

At the half-bridge operating mode, the AC power generation controller193 operates one of two half-bridge transistor circuits, and stops theoperation of the other. The AC power generation controller 193 turns offthe upper transistor of the half-bridge transistor circuit, theoperation of which is stopped, and turns on the lower transistor of thehalf-bridge transistor circuit. The AC power generation controller 193applies a control signal to the half-bridge transistor circuit, theoperation of which is allowed, as described with reference to FIG. 10.

At the full-bridge operating mode, the AC power generation controller193 alternately applies a control signal for one half period and acontrol signal for the other half period to the DC-AC converter 163.During one half period, the upper transistor T41 of one half-bridgetransistor circuit is turned on, and the lower transistor T42 thereof isturned off. The upper transistor T44 of the other half-bridge transistorcircuit is turned off, and the lower transistor T43 thereof is turnedon. During the other half period, the upper transistor T41 of onehalf-bridge transistor circuit is turned off, and the lower transistorT42 thereof is turned on. The upper transistor T44 of the otherhalf-bridge transistor circuit is turned on, and the lower transistorT43 thereof is turned off. Two transistor operating modes may besynchronized with a lower-power sine wave signal of the oscillator 130.In order to inhibit a short circuit occurring by simultaneously turningon the upper and the lower transistors, the upper and lower transistorcontrol signals may have a dead time slot.

According to another embodiment, the voltage difference measuring unit181 may obtain the measurement output current value based on thedifference between voltages applied to both terminals of the resistorR1, the DC power generation controller 191 may obtain a measurementoutput power value, which is a present output power value of the powersupply 110, based on the measurement output current value, and maydetermine the operating mode of the DC-AC converter 163 based on themeasurement output power value. In this case, the operating mode may beone of the full-bridge operating mode and the half-bridge operatingmode. The DC power generation controller 191 may compare the measurementoutput power value with the reference value and determine the operatingmode of the DC-AC converter 163 according to the comparison result. Inthis case, the reference value may be in the desirable current range oftable 2 set according to the initial output voltage value. If themeasurement output power value is greater than the reference value, theDC power generation controller 191 may determine the operating mode ofthe DC-AC converter 163 as a full-bridge operating mode. If themeasurement output power value is smaller than the reference value, theDC power generation controller 191 may determine the operating mode ofthe DC-AC converter 163 as the half-bridge operating mode.

The DC-AC converter 163 converts the output power of the power supply110 into the AC power having the rectangular-waveform AC voltage V3based on the AC power generation control signal (step S313), and outputsthe output power to the transmission induction coil unit 210.

The wireless power transmitting apparatus 200 transmits therectangular-waveform AC power having the rectangular-waveform AC voltageV3 to the wireless power receiving apparatus 300 by resonance (stepS315).

Hereinafter, a power supply device 100 according to still anotherembodiment will be described with reference to FIGS. 16 to 19.

FIG. 16 is a block diagram showing the power supply device 100 accordingto still another embodiment.

As shown in FIG. 16, the power supply device 100 according to stillanother embodiment includes a power supply 110, an oscillator 130, an ACpower generator 170, a power transmission state detector 180, and atransmit power controller 190. In addition, the power supply device 100is connected with the wireless power transmitting apparatus 200.

The power supply 110 generates DC power having DC voltage and outputsthe DC power through an output terminal thereof.

The oscillator 130 generates a lower-power sine wave signal.

The power transmission state detector 180 detects the wireless powertransmission state.

The transmit power controller 190 generates a control signal to controlthe AC power generator 170 based on the detected wireless powertransmission state and the lower-power sine wave signal of theoscillator 130.

The AC power generator 170 generates AC power havingrectangular-waveform voltage by amplifying the lower-power sine wavesignal of the oscillator 130 using DC power of the power supply 110according to the control signal of the transmit power controller 190.

The wireless power transmitting apparatus 200 transmits the output powerof the AC power generator 170 to the wireless power receiving apparatus300 by resonance.

FIG. 17 is a block diagram showing the AC power generator 170 and thetransmit power controller 190 according to still another embodiment.

As shown in FIG. 17, the AC power generator 170 according to stillanother embodiment includes a DC-DC converter 175 and a DC-AC converter173, and the transmit power controller 190 includes an DC powergeneration controller 191, a storage unit 192, and an AC powergeneration controller 193.

The DC power generation controller 191 generates a DC power generationcontrol signal based on the detected wireless power transmission stateso that the DC-DC converter 175 may output DC power having outputcurrent in a target current range and target DC voltage.

The storage unit 192 stores a look-up table.

The DC-DC converter 175 converts the output power of the power supply110 into the DC power, which has output current in the target currentrange and the target DC voltage, based on the DC power generationcontrol signal.

The AC power generation controller 193 generates an AC power generationcontrol signal based on the lower-power sine wave signal of theoscillator 130. In addition, the AC power generation controller 193 maygenerate the AC power generation control signal, which allows the DC-DCconverter 175 to output DC power having the output current in the targetcurrent range, based on the detected wireless power transmission state.The target current range may be the range of the peak-to-peak value ofthe target current.

The DC-AC converter 173 converts the output power of the DC-DC converter155 into the rectangular-waveform power based on the AC power generationcontrol signal, and outputs the power to the transmission induction coilunit 210.

FIG. 18 is a circuit diagram showing the DC-AC converter 173 and thepower transmission state detector 180 according to still anotherembodiment.

As shown in FIG. 18, the DC-AC converter 173 includes a full-bridgetransistor circuit unit. The full-bridge transistor circuit unitincludes two half-bridge transistor circuits. One of the two half-bridgetransistor circuits includes upper and lower transistors T61 and T62,and the other includes upper and lower transistors T64 and T63. Theupper transistors T61 and T64, and the lower transistors T62 and T63 maybe n-channel metal-oxide-semiconductor field-effect transistors(NMOS-FETs), and may be substituted with different devices performingthe same operation.

The power transmission state detector 180 includes a resistor R1 and thevoltage difference measuring unit 181, and is connected to the DC-DCconverter 175, the DC-AC converter 173, and the AC power generationcontroller 193. The DC-AC converter 173 is connected to the DC-DCconverter 175 through the resistor R1.

The AC power generation controller 193 has first and second uppertransistor control signal output terminals and first and second lowertransistor control signal output terminals, and generates an AC powergeneration control signal based on the lower-power sine wave signal ofthe oscillator 130 and a wireless power transmission state.

A drain electrode of the upper transistor T61 is connected with oneterminal of the resistor R1, a gate electrode of the upper transistorT61 is connected with the first upper transistor control signal outputterminal of the AC power generation controller 193, and a sourceelectrode of the upper transistor T61 is connected with one terminal ofthe inductor L1.

A drain electrode of the lower transistor T62 is connected with thesource electrode of the upper transistor T61, a gate electrode of thelower transistor T62 is connected to the first lower transistor controlsignal output terminal of the AC power generation controller 193, and asource electrode of the lower transistor T62 is connected with theground.

A drain electrode of the upper transistor T64 is connected with oneterminal of the resistor R1, a gate electrode of the upper transistorT64 is connected with the second upper transistor control signal outputterminal of the AC power generation controller 193, and a sourceelectrode of the upper transistor T64 is connected with an oppositeterminal of the inductor L1.

A drain electrode of the lower transistor T63 is connected with thesource electrode of the upper transistor T64, a gate electrode of thelower transistor T63 is connected to the second lower transistor controlsignal output terminal of the AC power generation controller 193, and asource electrode of the lower transistor T63 is connected with theground.

The voltage difference measuring unit 181 measures the differencebetween voltages applied to both terminals of the resistor R1.

Hereinafter, a wireless power transmitting method will be described withreference to FIG. 19 according to still another embodiment.

FIG. 19 is a flowchart showing the wireless power transmitting methodaccording to still another embodiment.

In particular, FIG. 19 shows the wireless power transmitting method toexplain the embodiments of FIGS. 16 to 18 in detail.

The power supply 110 generates DC power having DC voltage (step S501).In particular, the power supply 110 may convert AC power having ACvoltage into the DC power having DC voltage.

The oscillator 130 generates the lower-power sine wave signal (stepS503).

The power transmission state detector 180 detects the wireless powertransmission state (step S505). The power transmission state detector180 may detect the wireless power transmission state based on the levelof the output current of the DC-DC converter 175. Since the voltagesapplied to the both terminal of the resistor R1 are proportional to thelevel of the output current of the power supply 110, the voltagedifference measuring unit 181 of the power transmission state detector180 may detect the wireless power transmission state based on thedifferent between the voltages applied to both terminals of the resistorR1. Since the output current of the DC-DC converter 175 may not beconstantly maintained, the power transmission state detector 180 maymeasure the peak-to-peak value of the output current of the DC-DCconverter 175.

The DC power generation controller 191 generates a DC power generationcontrol signal based on the detected wireless power transmission stateso that the DC-DC converter 175 may output DC power having current inthe target current range and target DC voltage (step S507), and outputsthe DC power generation control signal to the gate electrode of thetransistor T11. Details of step S507 have already been described in stepS107.

The DC-DC converter 175 converts the output power of the power supply110 into DC power having the output current in the target current rangeand the target DC voltage based on the DC power generation controlsignal (step S509).

The AC power generation controller 193 generates the AC power generationcontrol signal allowing the DC-DC converter 175 to output DC powerhaving the output current in the target current range, based on thedetected wireless power transmission state (step S511), and outputs theAC power generation control signal to the DC-AC converter 173. Detailsof step S511 have already been described in step S311.

The DC-AC converter 173 converts the output power of the power supply110 into the AC power having the rectangular-waveform AC voltage V3based on the AC power generation control signal (step S513), and outputsthe output power to the transmission induction coil unit 210.

The wireless power transmitting apparatus 200 transmits therectangular-waveform AC power having the rectangular-waveform AC voltageV3 to the wireless power receiving apparatus 300 by resonance (stepS515).

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A wireless power transmitting apparatuswirelessly transmitting power to a wireless power receiving apparatus,the wireless power transmitting apparatus comprising: a detectordetecting a wireless power transmission state between the wireless powertransmitting apparatus and the wireless power receiving apparatus; atransmit power controller generating a control signal to controltransmit power based on the detected wireless power transmission state;an AC power generator generating an AC power using first DC power basedon the control signal; and a transmission induction coil unittransmitting the AC power to a transmission resonance coil through anelectromagnetic induction scheme.
 2. The wireless power transmittingapparatus of claim 1, wherein the AC power generator comprises: a DC-DCconverter converting the first DC power into second DC power; and aDC-AC converter converting the second DC power into the AC power.
 3. Thewireless power transmitting apparatus of claim 2, wherein the transmitpower controller comprises a DC power generation controller generating aDC power generation control signal based on the detected wireless powertransmission state, and the DC-DC converter converts the first DC powerinto the second DC power based on the DC power generation controlsignal.
 4. The wireless power transmitting apparatus of claim 3, whereinthe DC power generation controller changes a duty cycle of the DC powergeneration control signal based on the detected wireless powertransmission state.
 5. The wireless power transmitting apparatus ofclaim 2, wherein the DC-AC converter comprises a transistor circuit unithaving a half-bridge structure.
 6. The wireless power transmittingapparatus of claim 1, wherein the AC power generator comprises afull-bridge transistor circuit unit operating at a half-bridge operatingmode and a full-bridge operating mode, the transmit power controllercomprises an AC power generation controller determining one of thehalf-bridge operating mode and the full-bridge operating mode based onthe detected wireless power transmission state to generate an AC powergeneration control signal corresponding to the determined operatingmode, and the full-bridge transistor circuit unit converts second DCpower into the AC power based on the AC power generation control signal.7. The wireless power transmitting apparatus of claim 1, wherein thedetector detects the wireless power transmission state based on a levelof current of the transmit power.
 8. The wireless power transmittingapparatus of claim 7, wherein the detector detects the wireless powertransmission state based on a peak-to-peak level of the current of thetransmit power.
 9. The wireless power transmitting apparatus of claim 1,wherein the AC power is a rectangular-waveform power.
 10. A wirelesspower transmitting apparatus wirelessly transmitting power to a wirelesspower receiving apparatus, the wireless power transmitting apparatuscomprising: a transmission induction coil transmitting power appliedthereto to a transmission resonance coil through an electromagneticinduction scheme; a transistor circuit unit having a full-bridgestructure and connected to the transmission induction coil; a detectordetecting a wireless power transmission state between the wireless powertransmitting apparatus and the wireless power receiving apparatus; and atransmit power controller controlling the transistor circuit unit havingthe full-bridge structure based on the detected wireless powertransmission state.
 11. The wireless power transmitting apparatus ofclaim 10, wherein the transistor circuit unit having the full-bridgestructure operates at one of a half-bridge operating mode and afull-bridge operating mode, and the transmit power controller determinesone of the half-bridge operating mode and the full-bridge operating modebased on the detected wireless power transmission state and controls thetransistor circuit unit according to the determined operating mode. 12.The wireless power transmitting apparatus of claim 11, wherein thetransistor circuit unit having the full-bridge structure comprises: afirst transistor comprising a drain electrode having DC power appliedthereto and a source electrode connected to one terminal of thetransmission induction coil; a second transistor comprising a drainelectrode connected to the source electrode of the first transistor anda source electrode connected to a ground; a third transistor comprisinga drain electrode having the DC power applied thereto and a sourceelectrode connected to an opposite terminal of the transmissioninduction coil; and a fourth transistor comprising a drain electrodeconnected to the source electrode of the third transistor and a sourceelectrode connected to the ground.
 13. The wireless power transmittingapparatus of claim 12, wherein, at the half-bridge operating mode, thetransmit power controller turns off the third transistor, turns on thefourth transistor, turns on the first transistor and turns off thesecond transistor during one half period, and turns off the firsttransistor and turns on the second transistor during a remaining halfperiod.
 14. The wireless power transmitting apparatus of claim 12,wherein, at the full-bridge operating mode, the transmit powercontroller turns on the first and fourth transistors and turns off thesecond and third transistors during one half period, and turns off thefirst and fourth transistors and turns on the second and thirdtransistors during a remaining half period.